In mask and regulator assemblages known in the art, the mask seals against the user's face. When the user inhales, pressure in the oronasal face seal of the mask is lowered, relative to the ambient surroundings. This relative decrease in pressure causes the mechanism of the regulator to dispense oxygen into the oronasal face seal. In some cases, oxygen and diluting air from the ambient surroundings are jointly dispensed into the oronasal face seal. Regulators that deliver oxygen in response to the user's inhalation are sometimes termed “demand regulators,” and those which are able to deliver a mixture of oxygen and diluting air are sometimes termed “diluter-demand regulators.” Regulators are sometimes said to be operated in various “modes” such as “demand mode” or “diluter-demand mode.” Similar nomenclature is sometimes applied to the combination of mask and regulator, as well.
In various aviation applications using masks with diluter-demand regulators, the regulator must reliably deliver a specified quantity of oxygen when the cabin pressure altitude is at 10,000 ft. It is very difficult and impractical to design a conventional regulator so that the required quantity of oxygen is delivered at 10,000 ft, but no oxygen is delivered at slightly lower pressure altitudes where the ambient pressure is only slightly higher, such as approximately 5,000 to 8,000 ft cabin pressure altitude.
This difficulty is particularly acute in regulators that are designed in a sufficiently compact and light weight package to render them practical to be mounted directly on the user's oxygen mask.
Further, it is very difficult and impractical to design a conventional regulator with very low inhalation resistance in a sufficiently compact and light weight package to render it practical to be mounted directly on the user's oxygen mask. Thus, it is difficult or impractical to alleviate the increased work of breathing and resulting fatigue and discomfort of the user. It would also be desirable to provide an improved oxygen breathing mask that allows a relative decrease in pressure in the mask to trigger a regulator to dispense oxygen into the oronasal face seal of the mask, but that at the same time avoids unnecessary oxygen usage when the mask is worn but the supply of oxygen is not required, in order to conserve the oxygen supply.
The present invention addresses and solves these and other problems associated with oxygen mask pressure regulators which must operate both above and below 10,000 ft.